Fasciola hepatica in alpine dairy farming: prevalence trends, risk factors and associations with Salmonella Dublin seropositivity.

Fasciola hepatica impairs animal health and productivity in ruminants and has been associated with Salmonella Dublin infection, a zoonotic pathogen in cattle that causes diarrhea, abortions, and pneumonia. This work reassessed F. hepatica seroprevalence in Tyrolean dairy herds and investigated associations with alpine pasturing, the breed, S. Dublin occurrence and milk performance. In late autumn/early winter 2023, bulk tank milk samples from 3645 farms were tested using a commercial ELISA test (IDEXX Fasciolosis Verification Test, Montpellier, France). Binary logistic regression and linear mixed models were used to evaluate risk factors and production effects. Overall, 86.1% of herds were positive for Fasciola antibodies - an increase of 13.1% compared to 2005. Alpine pasturing was a significant risk factor (odds ratio [OR] 4.7), and S. Dublin-positive farms had higher odds of Fasciola-infection (OR = 9.0). In non-alpine grazing herds, all models showed that Fasciola-infection was significantly associated with reduced milk yield, while no such associations were observed in the population with alpine pasture management. However, breed-specific analysis among alpine-pastured cows showed significant negative associations on milk yield in Simmental (p = 0.041) and Brown Swiss (p = 0.039). These results reveal an increasing F. hepatica prevalence in Tyrol and highlight alpine pasturing as a major risk factor. The observed production losses and the strong link with S. Dublin emphasize the parasite`s broader economic and public health importance for dairy farms in the European Alps. From a practical perspective, there is a clear need for region-specific F. hepatica control strategies in alpine dairy systems, with particular focus on pasture management and herd-level surveillance.